In general, image retrieval is performed on a number of managed images. For example, Japanese Laid-open Patent Publication No. 2008-131377 discloses a technique of classifying images so as to manage the images. When image retrieval is performed, an image classified by a user is supplied to the user as a result of the retrieval.
Furthermore, Japanese Laid-open Patent Publication No. 2011-70408 discloses a technique of retrieving an image which matches a keyword through the Internet and associating the keyword and the image as a technique of collecting images. For example, an image classification device collects images in a plurality of HTML pages including a keyword and calculates image feature values of the images. Thereafter, the image classification device performs clustering on a plurality of images in accordance with a distribution characteristic in a feature space and stores images included in a cluster corresponding to small dispersion as images associated with a specified keyword.